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Refrigerant/Lubricant Mixture Boiling Heat Transfer Research at NIST.


pdf icon Refrigerant/Lubricant Mixture Boiling Heat Transfer Research at NIST. (942 K)
Kedzierski, M. A.

Future Trends in Mechanical Engineering, Research and Development, 16th National Convention of Mechanical Engineers and All India Seminar. Proceedings. September 29-30, 2000, 24-29 pp, 2000.

Keywords:

refrigerants; lubricants; heat transfer

Abstract:

This paper overviews the boiling heat transfer research of the recent few years at NIST (National Institute of Standards and Technology) on refrigerant/lubricant mixtures. The aim of the research was to fundamentally understand the effects of lubricant properties and bubble parameters on heat transfer performance. The magnitude of the effect of lubricant viscosity, miscibility, and concentration on the heat transfer has been quantified. The mechanistic cause of each effect was given based on a new theoretical interpretation and/or one from the literature. The NIST research illustrates that large improvements over pure Rl34a heat transfer can be obtained for Rl34a/lubricant mixtures with small lubricant mass fraction, high lubricant viscosity and a large critical solution temperature (CST). A mechanistic explanation for the observed R134a/lubricant boiling is provided. A fluorescence measurement technique is currently under development with the purpose of unlocking the mechanisms of the lubricant excess layer.